High Molecular Weight Chitosan-Complexed RNA Nanoadjuvant for Effective Cancer Immunotherapy

Abstract

Nucleic acid-based adjuvants have recently emerged as promising candidates for use in cancer vaccines to induce tumor-suppressing immune cells. In this study, we tested whether complexation of a nucleic acid-based adjuvant with chitosan (CTS) modulates immune adjuvant functions. As a nucleic acid-based adjuvant, we used toll-like receptor 3-recognizing RNA adjuvant (RA). Negatively charged RA formed nanoscale polyplexes with cationic CTS that possessed positive zeta potentials. RA/CTS polyplexes exerted dendritic cell (DC)-maturation effects without causing significant DC toxicity. This DC-maturation effect was CTS molecular weight dependent, with RA/CTS polyplexes with a CTS molecular weight of 340 kDa (RA/CTS 340K) producing the greatest effect. Subcutaneous injection of RA/CTS 340K polyplexes with the model tumor antigen ovalbumin exerted a preventive effect against challenge by ovalbumin-expressing tumor cells. It also provided greater inhibitory effects against a second challenge with the same tumor cells compared with other treatments. These protective effects of subcutaneous RA/CTS polyplex treatment were associated with the highest tumor antigen-specific humoral and cellular immune responses after tumor challenge, and with the greatest infiltration of CD4 helper T cell and CD8 T cell into the tumor tissues. Mice vaccinated with ovalbumin and RA/CTS polyplexes showed complete survival, even after repeated challenge with tumor cells. Our results suggest the potential of RA/CTS polyplexes as effective nanoadjuvants in the design of tumor vaccines and cancer immunotherapy.

State-of-the-Art of Nanodiagnostics and Nanotherapeutics against SARS-CoV-2

“… 24 Cationic NPs could be used for entrapment or encapsulation of anionic DNA or RNA vaccines. 143 , 157 , 158 Very recently, a SARS-CoV-2 vaccine (mRNA-1273, by Moderna) has shown around 95% efficacy in Phase III clinical trials. The formulation is lipid NP-based and could be kept in regular freezers or refrigerators.…”

Lipid Nanoparticle-Mediated Lymphatic Delivery of Immunostimulatory Nucleic Acids

“…The particle size was measured over 1 week. The complexation of PIC and M-NP was analyzed by gel retardation assay [8]. PIC/M-NP were prepared by mixing PIC with M-NP at various weight ratios, followed by 1% agarose gel electrophoresis and analysis using a Gel Doc XR+ Imaging System (Bio-Rad, Hercules, CA, USA).…”

“…However, a subunit vaccine alone often fails to induce a strong immune response [5]. Aluminum-containing adjuvants have the longest history of use [6,7], but they have a limited ability to induce cellular immunity and thus are not suitable for intracellular antigen applications [8]. In addition, aluminum adjuvants can have some side effects, raising safety issues [6,9].…”

“…Adjuvants composed of nucleic acids have great advantages in terms of biocompatibility and safety [8]. The Toll-like receptor 9-agonizing nucleic acid, CpG 1018, is included as an adjuvant in the hepatitis B vaccine, HEPLISAV-B ® , which was recently approved by the U.S. FDA [10].…”

“…Although this supported the efficacy of nucleic acid adjuvants, the pharmaceutical application of nucleic acids has faced some limitations. For example, many nucleic acid adjuvants target intracellular molecules in immune-stimulating pathways and thus must be introduced into dendritic cells (DC) [8]. In addition, nucleic acids have weak stability due to the action of in vivo nucleases [11].…”